Ancelotti should have done what you said and I totally agree with that. Arda Guller was rarely played despite Ancelotti's reasoning for what he did to show how fierce the competition was for a place in the main line-up.
Camavinga often plays in the defender position even though there are other players whose main position is in defense.
I look forward to seeing Xabi Alonso's ingenuity at Real Madrid as a coach.
Ancelloti had his own tactics and one thing I notice is that he doesn’t like to trust or should we use a kinder word of he doesn’t want to rush the younger players into the first team. The likes of Arder Guler, Endrick, Ibrahim Diaz were in the shadow because of this, even Raul Acensio got the advantage of actually playing due to the number of injury crisis the team had. We can say that Real Madrid players weren’t at their best because of injuries or form but there was some games were I feel Ancelloti let them down. Like most of the el Classico games.
Alonso will tactically upgrade this team in my opinion because he seems to use a pattern that favours the young players more and that is what Real Madrid need at the moment